To date, in order to improve visibility from the driver's seat in a wheel loader, improvements in the shape of a bucket boom (also called a lift arm or lift link) included in a working equipment have been proposed (see patent documents 1 and 2). Specifically, a bucket attached to the front of such a working equipment, especially its left and right ends, is designed to be easily visible from the driver's seat, so that the position of the bucket with respect to the dump vessel can be quickly determined when loading soil into a dump, whereby operation(s) can be favorably carried out.
Specifically, according to the patent document 1, a bucket boom including a pair of left and right members is designed such that base ends of the members are coupled to a front frame while their distal ends are coupled to the bucket. By designing an interval between the members at their base ends to be smaller than an interval at their distal ends, a link mechanism is arranged not to widely spread out to the left and right at a side adjacent the front frame, thereby improving visibility.
On the other hand, according to the patent document 2, while the base ends and distal ends of the left and right members are respectively coupled to the front frame and the bucket, the interval between the distal ends of the members and the interval between their base ends are designed to be substantially equal. However, the interval between the members is narrowed in substantially the middle of each of the members in the front-rear direction, whereby visibility is improved. In other words, while a traditional arrangement is designed such that crossmembers connecting the members at their middles are positioned at the exact height of the dump vessel when the bucket boom is raised (lifted up) and thus blocks the bucket located to the front, the arrangement according to the patent document 2 is designed such that, by reducing the interval between the members at their middles, the left and right ends of the bucket can be reliably seen from the driver's seat even when the bucket is raised.
Patent Document 1: Japanese Patent No. 3730291
Patent Document 2: JP-A-2003-184122